Ofdm transmission/reception device for transmitting and receiving ofdm symbols having a variable data transmission rate and method thereof

ABSTRACT

An orthogonal frequency division multiplexing (OFDM) transmission device transmits OFDM symbols to at least one reception device and includes an OFDM transmission processing unit which generates a plurality of OFDM symbols; a pilot insertion unit which inserts pilot tones into each of the plurality of OFDM symbols; and a control unit which controls the pilot insertion unit to insert the pilot tones according to a pilot insertion pattern which is selected to correspond to a communication environment from among a plurality of pilot insertion patterns.

This application is a Divisional Application of U.S. application Ser.No. 12/601,857, which was filed on Nov. 25, 2009, and is a NationalStage of International Application No. PCT/KR2008/002473 filed Apr. 30,2008 and claims priority Korean Patent Application No. 10-2007-0051724filed on May 28, 2007, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to orthogonal frequency divisionmultiplexing (OFDM) transmission and reception devices and methodsthereof. More particularly, the present invention relates to OFDMtransmission and reception devices which transmit and receive OFDMsymbols having a variable data transmission rate, and to methodsthereof.

2. Description of the Related Art

With the development of electronic and communication technologies,digital technologies have been introduced into the field of broadcastingsystems, and diverse standards for digital broadcasting have beenpublished. Specific examples of such standards are the U.S.-orientedAdvanced Television Systems Committee Vestigial Sideband (ATSC VSB)standard and the European-oriented Digital VideoBroadcasting-Terrestrial (DVB-T) standard. These two standards differfrom each other in many ways, such as the manner of audio compressionand the channel bands employed. In particular, ATSC VSB standards employsingle carrier schemes, but DVB-T standards employ multiple carrierschemes.

The multiple carrier schemes employed in DVB-T standards is anorthogonal frequency division multiplexing (OFDM) scheme. OFDM schemesare utilized as standards for IEEE 802.11a, ETSI BRAN'S HIPERLAN 2,European digital audio broadcasting (DAB) and digital TV DVB-T. Aconventional single carrier transmission scheme in which information iscarried by a single carrier causes interference between symbols toincrease, so distortion also increases. Accordingly, an equalizer of areceiver must be complicated. In order to solve these problems of theconventional single carrier transmission scheme, OFDM schemes have beenintroduced.

OFDM schemes enable data to be transmitted using multi-carriers. SuchOFDM schemes are able to convert data symbols input in series intoparallel data symbols, to modulate each of the parallel symbols into aplurality of tone signals which are orthogonal to each other, and totransmit the modulated signals.

OFDM schemes have been widely applied to digital transmissiontechnologies, such as Digital Audio Broadcasting (DAB), digitaltelevision, Wireless Local Area Network (WLAN) or Wireless AsynchronousTransfer Mode (WATM). In particular, OFDM schemes maintain orthogonalitybetween tone signals, unlike conventional multi-carrier schemes, so itis possible to obtain optimum transmission efficiency during high speeddata transmission. Additionally, almost the entire available frequencyband can be utilized and multi-path fading can be reduced.

In a DVB-T system, pilot tones are inserted into OFDM symbols, and theOFDM symbols into which the pilot tones are inserted are transmitted toa reception device, so that the reception device may perform channelequalization and estimation. The number of pilot tones to be used may bedetermined according to the type of standard. For example, 142 pilottones may be used in a 2K Fast Fourier Transform (FFT) transmissionmode, and 568 pilot tones may be used in an 8K FFT transmission mode.The capacity of pilot tones corresponds to approximately 8.3% of thetotal data transmission capacity.

The reception device checks the pilot tones inserted into the OFDMsymbols, to analyze the noise of channels, so as to perform channelequalization. The pilot tones are inserted into the OFDM symbolsaccording to regular pilot insertion patterns, which are shared betweenthe reception device and transmission device.

A conventional DVB-T system has the advantage that it is able to receivesignals while moving, because channel estimation information is rapidlyupdated by frequent insertion of pilot tones in a time shaft. However,excess pilot insertion causes a reduction in the capacity of data to beactually transmitted.

If a reception device is fixed in place so that it hardly moves, thereare not many changes in the time characteristics of channels formedbetween the reception device and transmission device.

However, even in this situation, pilot tones are inserted into OFDMsymbols in the conventional DVB-T system without changing the pilotinsertion pattern, so the data transmission rate is reducedunnecessarily.

SUMMARY OF THE INVENTION

The present invention provides orthogonal frequency divisionmultiplexing (OFDM) transmission and reception devices which are able totransceive OFDM symbols having a variable data transmission rate inorder to efficiently transmit data, and methods thereof.

The present invention also provides orthogonal frequency divisionmultiplexing (OFDM) transmission and reception devices which are able totransceive data by variably adjusting the data transmission rate whileutilizing an original system used as an OFDM transceiver, and methodsthereof.

According to an aspect of the present invention, there is provided anorthogonal frequency division multiplexing (OFDM) transmission devicewhich transmits OFDM symbols to at least one reception device, the OFDMtransmission device including an OFDM transmission processing unit whichgenerates a plurality of OFDM symbols; a pilot insertion unit whichinserts pilot tones into each of the plurality of OFDM symbols; and acontrol unit which controls the pilot insertion unit to insert the pilottones according to a pilot insertion pattern which is selected tocorrespond to a communication environment from among a plurality ofpilot insertion patterns.

The control unit may control the pilot insertion unit to insert thepilot tones into only some of the plurality of OFDM symbols, if a staticcommunication environment is established in which the at least onereception device receives the plurality of OFDM symbols while beingfixed in place.

The control unit may control the pilot insertion unit to insert thepilot tones into each of the plurality of OFDM symbols, if a dynamiccommunication environment is established in which the at least onereception device receives the plurality of OFDM symbols while moving.

The control unit may select one from among a first pilot insertionpattern in which pilot tones are inserted into only one OFDM symbolamong every three OFDM symbols, a second pilot insertion pattern inwhich pilot tones are inserted into only two OFDM symbols among everythree OFDM symbols, a third pilot insertion pattern in which pilot tonesare inserted into four OFDM symbols among every five OFDM symbols, and afourth pilot insertion pattern in which pilot tones are inserted intoall of the plurality of OFDM symbols, and may control the pilotinsertion unit to insert the pilot tones into the plurality of OFDMsymbols according to the selected pilot insertion pattern.

The OFDM transmission device may further include a storage unit whichstores information regarding the first to fourth pilot insertionpatterns; and an input unit which inputs information regarding thecommunication environment. The control unit may select a pilot insertionpattern corresponding to the information regarding the communicationenvironment received from the input unit, and the pilot insertion unitmay read information regarding the selected pilot insertion pattern fromthe storage unit and insert the pilot tones based on the readinformation.

The pilot insertion unit may insert each pilot tone into a single OFDMsymbol every twelfth tone so that the pilot tone on the OFDM symbol maybe spaced apart from a pilot tone on a previous OFDM symbol by threetones.

The control unit may control the pilot insertion unit to insert eachpilot tone in each preset pilot insertion position on only some of theplurality of OFDM symbols according to the type of communicationenvironment.

The pilot insertion unit may insert each pilot tone into a single OFDMsymbol every n-th tone so that the pilot tone on the OFDM symbol may bespaced apart from a pilot tone on a previous OFDM symbol by m tones.Here, n and m may be natural numbers.

The control unit may change the pilot insertion pattern by adjusting atleast one of n and m according to the type of communication environment.

The control unit may control the pilot insertion unit to insert eachpilot tone in each preset pilot insertion position on only some of theplurality of OFDM symbols according to the type of communicationenvironment, if n and m are fixed values.

The control unit may notify the at least one reception device of theinformation regarding the selected pilot insertion pattern via datatones in at least one OFDM symbol among the plurality of OFDM symbols.

According to another aspect of the present invention, there is providedan orthogonal frequency division multiplexing (OFDM) transmission methodwhich transmits OFDM symbols to at least one reception device, the OFDMtransmission method including generating a plurality of OFDM symbols;selecting one pilot insertion pattern from among a plurality of pilotinsertion patterns according to the type of communication environmentwith the at least one reception device; inserting pilot tones into eachof the plurality of OFDM symbols according to the selected pilotinsertion pattern; and transmitting the plurality of OFDM symbols to theat least one reception device.

The selecting may include selecting a pilot insertion pattern in whichpilot tones are inserted into only some of the plurality of OFDMsymbols, if a static communication environment is established in whichthe at least one reception device receives the plurality of OFDM symbolswhile being fixed in place.

The selecting may include selecting a pilot insertion pattern in whichpilot tones are inserted into each of the plurality of OFDM symbols, ifa dynamic communication environment is established in which the at leastone reception device receives the plurality of OFDM symbols whilemoving.

The selecting may include selecting one from among a first pilotinsertion pattern in which pilot tones are inserted into only one OFDMsymbol among every three OFDM symbols, a second pilot insertion patternin which pilot tones are inserted into only two OFDM symbols among everythree OFDM symbols, a third pilot insertion pattern in which pilot tonesare inserted into four OFDM symbols among every five OFDM symbols, and afourth pilot insertion pattern in which pilot tones are inserted intoall of the plurality of OFDM symbols, according to the type ofcommunication environment.

The inserting may include inserting each pilot tone into a single OFDMsymbol every twelfth tone so that the pilot tone on the OFDM symbol maybe spaced apart from a pilot tone on a previous OFDM symbol by threetones.

The inserting may include inserting each pilot tone in each preset pilotinsertion position on only some of the plurality of OFDM symbolsaccording to the type of communication environment.

The inserting may include inserting each pilot tone into a single OFDMsymbol every n-th tone so that the pilot tone on the OFDM symbol may bespaced apart from a pilot tone on a previous OFDM symbol by m tones.Here, n and m may be natural numbers.

The selecting may include selecting one from among the plurality ofpilot insertion patterns by adjusting at least one of n and m accordingto the type of communication environment.

The selecting may include selecting a pilot insertion pattern in whicheach pilot tone is inserted in each preset pilot insertion position ononly some of the plurality of OFDM symbols according to the type ofcommunication environment, if n and m are fixed values.

The OFDM transmission method may further include notifying the at leastone reception device of information regarding the selected pilotinsertion pattern via data tones in at least one OFDM symbol among theplurality of OFDM symbols.

According to another aspect of the present invention, there is providedan orthogonal frequency division multiplexing (OFDM) reception device,the OFDM reception device including a receiving unit which receives aplurality of OFDM symbols, of which the data transmission rate variesaccording to changes in pilot insertion patterns; a pilot insertionpattern determination unit which detects pilot insertion patterninformation contained in the plurality of OFDM symbols, and determineswhich pilot insertion pattern is used in the plurality of OFDM symbolsusing the detected information; and an OFDM reception processing unitwhich detects pilot tones from the plurality of OFDM symbols based onthe determined pilot insertion pattern, and processes the plurality ofOFDM symbols.

The OFDM reception device may further include a storage unit whichstores pilot insertion pattern information which is shared with an OFDMtransmission device. In this situation, the pilot insertion patterndetermination unit may read the pilot insertion pattern information fromthe storage unit.

The reception unit may receive a plurality of OFDM symbols, only some ofwhich contain pilot tones, if a static communication environment isestablished in which the OFDM reception device receives the plurality ofOFDM symbols while being fixed in place. The reception unit may receivea plurality of OFDM symbols, each of which contains pilot tones, if adynamic communication environment is established in which the OFDMreception device receives the plurality of OFDM symbols while moving.

The pilot tones may be inserted into the plurality of OFDM symbolsaccording to one selected from among a first pilot insertion pattern inwhich pilot tones are inserted into only one OFDM symbol among everythree OFDM symbols, a second pilot insertion pattern in which pilottones are inserted into only two OFDM symbols among every three OFDMsymbols, a third pilot insertion pattern in which pilot tones areinserted into four OFDM symbols among every five OFDM symbols, and afourth pilot insertion pattern in which pilot tones are inserted intoeach of the plurality of OFDM symbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every twelfth tone so that the pilot tone onthe OFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by three tones. If pilot insertion is skipped with respect toonly some of the plurality of OFDM symbols according to the type ofcommunication environment, each pilot tone may be inserted in the setpilot insertion position on the remainder of the plurality of OFDMsymbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every n-th tone so that the pilot tone on theOFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by m tones. Here, n and m may be natural numbers. If pilotinsertion is skipped with respect to only some of the plurality of OFDMsymbols according to the type of communication environment, each pilottone may be inserted in the set pilot insertion position on theremainder of the plurality of OFDM symbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every n-th tone so that the pilot tone on theOFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by m tones. Here, n and m may be natural numbers. Pilot tones maybe inserted according to a pilot insertion pattern in which at least oneof n and m is adjusted corresponding to the type of communicationenvironment.

According to another aspect of the present invention, there is providedan orthogonal frequency division multiplexing (OFDM) reception method inan OFDM reception device, the OFDM reception method including receivinga plurality of OFDM symbols, of which the data transmission rate variesaccording to changes in pilot insertion patterns; detecting pilotinsertion pattern information contained in the plurality of OFDMsymbols, and determining which pilot insertion pattern is used in theplurality of OFDM symbols using the detected information; and detectingpilot tones from the plurality of OFDM symbols based on the determinedpilot insertion pattern, and processing the plurality of OFDM symbols.

The detecting and processing may include reading pilot insertion patterninformation which is previously stored and are shared with an OFDMtransmission device.

The receiving may include receiving a plurality of OFDM symbols, onlysome of which contain pilot tones, if a static communication environmentis established in which the OFDM reception device receives the pluralityof OFDM symbols while being fixed in place; and receiving a plurality ofOFDM symbols, each of which contains pilot tones, if a dynamiccommunication environment is established in which the OFDM receptiondevice receives the plurality of OFDM symbols while moving.

The pilot tones may be inserted into the plurality of OFDM symbolsaccording to one selected from among a first pilot insertion pattern inwhich pilot tones are inserted into only one OFDM symbol among everythree OFDM symbols, a second pilot insertion pattern in which pilottones are inserted into only two OFDM symbols among every three OFDMsymbols, a third pilot insertion pattern in which pilot tones areinserted into four OFDM symbols among every five OFDM symbols, and afourth pilot insertion pattern in which pilot tones are inserted intoall of the plurality of OFDM symbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every twelfth tone so that the pilot tone onthe OFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by three tones. If pilot insertion is skipped with respect toonly some of the plurality of OFDM symbols according to the type ofcommunication environment, each pilot tone may be inserted in the setpilot insertion position on the remainder of the plurality of OFDMsymbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every n-th tone so that the pilot tone on theOFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by m tones. Here, n and m may be natural numbers. If pilotinsertion is skipped with respect to only some of the plurality of OFDMsymbols according to the type of communication environment, each pilottone may be inserted in the set pilot insertion position on theremainder of the plurality of OFDM symbols.

Each pilot insertion position may be set by inserting each pilot toneinto a single OFDM symbol every n-th tone so that the pilot tone on theOFDM symbol may be spaced apart from a pilot tone on a previous OFDMsymbol by m tones. Here, n and m may be natural numbers. Pilot tones maybe inserted according to a pilot insertion pattern in which at least oneof n and m is adjusted corresponding to the type of communicationenvironment.

As described above, according to the present invention, a pilotinsertion pattern is adaptively selected according to the type ofcommunication environment, so it is possible to variably adjust the datatransmission rate. Accordingly, the number of times unnecessary pilottones are transmitted may be reduced, and it is thus possible totransceive data more efficiently.

Additionally, it is possible to adjust a pilot insertion period and adistance between pilot insertion positions of each OFDM symbol.Accordingly, if the pilot insertion period and distance are setaccording to a conventional standard, a system according to the presentinvention may be desired in the same manner as a conventional systememploying the conventional standard, so it is possible to increase thedata transmission rate while utilizing the conventional system. In otherwords, the OFDM transmission and reception devices have compatibilitywith conventional OFDM transmission and reception devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and advantages of the present invention willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a block diagram showing an orthogonal frequency divisionmultiplexing (OFDM) transmission device according to an exemplaryembodiment of the present invention;

FIG. 2 is a detailed block diagram showing the OFDM transmission deviceof FIG. 1;

FIGS. 3 to 6 illustrate examples of various pilot insertion patterns inwhich pilot tones are inserted into OFDM symbols transmitted by the OFDMtransmission device of FIG. 1;

FIG. 7 is a flowchart explaining an OFDM transmission method accordingto an exemplary embodiment of the present invention;

FIG. 8 is a block diagram showing an OFDM reception device according toan exemplary embodiment of the present invention;

FIG. 9 is a detailed block diagram showing the OFDM reception device ofFIG. 8;

FIG. 10 is a flowchart explaining an OFDM reception method according toan exemplary embodiment of the present invention; and

FIGS. 11 and 12 illustrate examples of various pilot insertion patternswhich are applicable to OFDM symbols transceived between the OFDMtransmission device and the OFDM reception device.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an orthogonal frequency divisionmultiplexing (OFDM) transmission device according to an exemplaryembodiment of the present invention. The OFDM transmission device ofFIG. 1 includes an OFDM transmission processing unit 110, a pilotinsertion unit 120 and a control unit 130.

The OFDM transmission processing unit 110 generates a plurality of OFDMsymbols to be transmitted to an OFDM reception device (not shown). Inmore detail, if transport streams (TS) are received from a broadcastingapparatus, the OFDM transmission processing unit 110 modulates thereceived TS on a plurality of sub-carriers, to generate a plurality ofOFDM symbols. The configuration of the OFDM transmission processing unit110 will be described in detail later.

The control unit 130 selects a pilot insertion pattern according to thecommunication environment between the OFDM transmission device and anOFDM reception device. Specifically, the control unit 130 may select onepilot insertion pattern corresponding to the current communicationenvironment from among a plurality of pilot insertion patterns that havebeen previously set between the OFDM transmission device and OFDMreception device. For example, if a dynamic communication environment isestablished, that is, if an OFDM reception device receives a broadcastwhile moving, the control unit 130 may select a pilot insertion patternin which a large number of pilot tones are used. Alternatively, if astatic communication environment is established, that is, if an OFDMreception device that is unable to move receives a broadcast, thecontrol unit 130 may select a pilot insertion pattern in which a smallnumber of pilot tones are used.

The type of communication environment may be determined by taking intoconsideration the characteristics of a system to which an OFDMtransmission mode is applied. For example, in the case of a system totransmit High-Definition (HD) grade broadcasting data, HD gradebroadcasting data has a larger capacity than Standard-Definition (SD)grade broadcasting data, and thus requires an increase in the datatransmission rate. Accordingly, a pilot insertion pattern in which arelatively small number of pilot tones is used may be selected, such asa static communication environment.

The pilot insertion unit 120 inserts pilot tones into the plurality ofOFDM symbols generated by the OFDM transmission processing unit 110.Here, the pilot insertion unit 120 may insert each pilot tone intopositions of the OFDM symbols set according to the pilot insertionpattern selected by the control unit 130. A pilot insertion process hasbeen published in the DVB-T standard, so detailed description thereof isomitted.

FIG. 2 is a detailed block diagram showing the OFDM transmission deviceof FIG. 1. The OFDM transmission device further includes a storage unit140 and an input unit 150, in addition to the OFDM transmissionprocessing unit 110, pilot insertion unit 120 and control unit 130.

The OFDM transmission processing unit 110 generates a plurality of OFDMsymbols and transmits the generated OFDM symbols to a reception devicevia an antenna. The OFDM transmission processing unit 110 includes ascrambler 111, a Forward Error Correction (FEC) encoder 112, a mapper113, an Inverse Fast Fourier Transform (IFFT) processing unit 114 and adigital-to-analog converter (DAC) 115.

The scrambler 111 randomizes data to be transmitted.

The FEC encoder 112 detects errors that occurs in a reception device andperforms encoding on OFDM data to collect the detected errors.Specifically, the FEC encoder 112 performs encoding includingconvolutional encoding and Reed-Solomon (RS) encoding.

The mapper 113 maps the coded OFDM data using a symbol constellation,such as Quadrature Phase Shift Keying (QPSK), 16-Quadrature AmplitudeModulation (QAM) or 64-QAM. In the case of general DVB-T transmissionsystems, the 64-QAM constellation is used. If a TV transmission mode isactivated in the DVB-T transmission system, the mapper 113 uses a symbolconstellation in which inphase (I) and quadrature (Q) components of theOFDM symbols are regularly projected at coordinates of (−7, −5, −3, −1,1, 3, 5, 7).

The IFFT processing unit 114 performs IFFT processing, so that frequencydomain OFDM signals are converted into time domain OFDM signals. In moredetail, the IFFT processing unit 114 allocates frequency domain OFDMsignals comprising a plurality of pieces of parallel data to a pluralityof sub-carriers, modulates the frequency domain OFDM signals and outputstime domain OFDM symbols.

The pilot insertion unit 120 generates pilot tone signals for the I andQ components of the OFDM signal, and transmits the generated pilot tonesignals to the IFFT processing unit 114. Accordingly, the IFFTprocessing unit 114 may perform IFFT processing, so that the pilot tonesignals may be disposed in each position within the OFDM symbols.

The DAC 115 performs digital-to-analog conversion on the OFDM symbolsoutput from the IFFT processing unit 114, so that these OFDM symbols aretransmitted to the reception device via the antenna.

Although not shown in FIG. 2, the OFDM transmission processing unit 110may further include a guard interval (GI) insertion unit which insertsGIs into the leading end of each OFDM symbol, a synchronizationinformation insertion unit which inserts timing synchronization signalsand Pseudo-random Noise (PN) sequences into the front of the GIs, afilter unit which filters the OFDM symbols into which the PN sequencesare inserted so that the OFDM symbols display predetermined waveforms,and a radio frequency (RF) processing unit which transmits the filteredOFDM symbols via wireless channels. As described above, theconfiguration of the OFDM transmission processing unit 110 may differamong various exemplary embodiments of the present invention.

The storage unit 140 stores a plurality of pilot insertion patterns. TheOFDM transmission device according to the exemplary embodiment of thepresent invention shares the pilot insertion patterns with an OFDMreception device (not shown). Each of the plurality of pilot insertionpatterns may be stored matching the type of communication environment.For example, if a communication environment where a data transmissionrate is important is established, a pilot insertion pattern in whichpilot tones are inserted into only some OFDM symbols may be used.Alternatively, if a communication environment which requires stable datareception is formed, for example, a dynamic communication environment, apilot insertion pattern, in which pilot tones are individually insertedinto each of the OFDM symbols, may be used.

The control unit 130 selects one from among the plurality of pilotinsertion patterns stored in the storage unit 140, and controls thepilot insertion unit 120 to insert pilot tones into OFDM symbols inaccordance with the selected pilot insertion pattern.

In more detail, the control unit 130 may receive information regardingthe communication environment from the input unit 150. In response to atransmitter selection signal input by the input unit 150, the controlunit 130 may select one from among the plurality of pilot insertionpatterns. Alternatively, the input unit 150 may be implemented as aninterface capable of receiving information or request regarding thecommunication environment from the OFDM reception device. In thissituation, the control unit 130 may select a pilot insertion pattern inresponse to the request by the OFDM reception device through the inputunit 150.

The plurality of pilot insertion patterns stored in the storage unit 140generally comply with the DVB-T standard. Accordingly, each pilot toneis inserted on a single OFDM symbol in a predetermined period, forexample every twelfth tone. In this situation, a pilot tone on a currentOFDM symbol is spaced apart from a pilot tone on a previous OFDM symbolby two tones. In order to increase the data transmission rate, a pilotinsertion pattern may be designed in which pilot insertion is skippedwith respect to only some OFDM symbols. In this situation, pilot tonesare inserted in a preset position of remaining OFDM symbols, so the OFDMtransmission device according to the present exemplary embodiment mayperform pilot insertion and pilot detection in the conventional DVB-Ttransmission system without change.

FIGS. 3 to 6 exemplarily show various pilot insertion patterns, and showonly some of the plurality of OFDM symbols which are continuouslytransmitted. In FIGS. 3 to 6, a horizontal axis indicates a frequency,so a single line on the horizontal axis represents a single OFDM symbol;and a vertical axis indicates time, so the plurality of OFDM symbols maybe transmitted in sequence as time passes. Additionally, white positionsindicate data tones, and black tones indicate pilot tones that areinserted into OFDM symbols. In order to facilitate understanding of thepresent invention, OFDM symbols shown in FIGS. 3 to 6 are referred to assymbol 1, symbol 2, symbol 3, . . . , and symbol n, sequentially fromtop to bottom. Furthermore, the leftmost position of a single OFDMsymbol is referred to as position Kmin, and the rightmost position isreferred to as position Kmax. While both positions Kmin and Kmax containpilot tones as shown in FIGS. 3 to 6, there is no limitation thereto.

FIG. 3 shows a pilot insertion pattern, in which pilot tones areinserted into only one OFDM symbol and pilot insertion is skipped withrespect to two OFDM symbols among every three OFDM symbols, and which ishereinbelow referred to as a first pilot insertion pattern. Here, pilottones are inserted into position Kmax and position Kmin at all times.

As shown in the first pilot insertion pattern of FIG. 3, a second pilottone is inserted into the twelfth position from position Kmin on thefirst OFDM symbol (namely, symbol 1), and a third pilot tone is insertedinto the twelfth position from the second pilot tone. Accordingly, pilottones may be inserted into every twelfth position on a single OFDMsymbol.

According to the first pilot insertion pattern of FIG. 3, pilot tonesare not inserted into a second symbol and a third symbol, namely symbol2 and symbol 3, excluding positions Kmin and Kmax, and pilot tones areinserted into a fourth symbol. On the fourth symbol, a second pilot toneis inserted into a ninth position from position Kmin. For example, if apilot tone is inserted into a third position from position Kmin on thesecond symbol and if a pilot tone is inserted into a sixth position fromposition Kmin on the third symbol, a pilot tone may be inserted into theninth position from position Kmin on the fourth symbol without change.Accordingly, it is possible to achieve compatibility with a conventionalDVB-T system. Pilot tones are inserted into other OFDM symbols in thesame manner as described above.

FIG. 4 shows a pilot insertion pattern in which pilot tones are insertedinto two OFDM symbols among every three OFDM symbols, and moreparticularly, in which pilot tones are not inserted into positions,excluding positions Kmin and Kmax, on a third, sixth, ninth, . . . ,3N-th OFDM symbols. This pilot insertion pattern is hereinbelow referredto as a second pilot insertion pattern.

FIG. 5 shows a pilot insertion pattern in which pilot tones are insertedinto four OFDM symbols among every five OFDM symbols, and moreparticularly, in which pilot tones are not inserted into positions,excluding positions Kmin and Kmax, on a first, sixth, eleventh, . . . ,(5N-4)-th OFDM symbols. This pilot insertion pattern is hereinbelowreferred to as a third pilot insertion pattern.

FIG. 6 shows a pilot insertion pattern in which pilot tones are insertedinto all OFDM symbols. Each of pilot tones inserted into a certainsymbol is placed rightward by three tones from each of pilot tonesinserted into a previous symbol. The pilot insertion pattern shown inFIG. 6 may be employed in a dynamic communication environment, andhereinafter, is referred to as a fourth pilot insertion pattern.

Pilot tones that are not inserted into OFDM symbols in the pilotinsertion patterns shown in FIGS. 3 to 6 are used as data tones.Comparing each of the pilot insertion patterns, the position of pilottones inserted into OFDM symbols remains unchanged on the time axis,except that pilot tones are not inserted into some OFDM symbols. Thesepilot insertion patterns comply with a conventional DVB-T standard, soit is possible for the system according to the exemplary embodiment tohave compatibility with a conventional DVB-T system.

Kmax in the pilot insertion patterns shown in FIGS. 3 to 6 is 1704 undera 2K FFT mode set using the DVB-T standard, so 1704 tone signals mayform a single symbol. Additionally, Kmax in the pilot insertion patternsshown in FIGS. 3 to 6 is 6816 under a 8K FFT mode set using the DVB-Tstandard, so 6816 tone signals may form a single symbol. If pilot tonesare inserted in the same manner as the fourth pilot insertion pattern,142 tones of the 1704 tones are used as pilot tones under the 2K FFTmode, and 568 tones of the 6816 tones are used as pilot tones under the8K FFT mode. This corresponds to 8.3% of the total data transmissionrate. Accordingly, one of the first to third pilot insertion patternsmay be selectively used to reduce the ratio of pilot tones to totaltones, so it is possible to increase the data transmission rate.

The control unit 130 selects one from among the first to fourth pilotinsertion patterns according to the communication environment, andcontrols the pilot insertion unit 120 to insert pilot tones into OFDMsymbols in the selected pattern. For example, the control unit 130 mayselect the fourth pilot insertion pattern matching the dynamiccommunication environment. Alternatively, if HD grade broadcasting datais transmitted to a fixed reception device, the control unit 130 mayselect the first pilot insertion pattern. Additionally, it is possiblefor the control unit 130 to select one from among the first to fourthpilot insertion patterns, taking into consideration the amount of datato be transmitted or the stability, and to adopt the selected pattern.

As described above, the pilot insertion patterns may be selected inresponse to the transmitter selection signal or the request by thereceiver input by the input unit 150.

The control unit 130 needs to notify the OFDM reception device of whichpilot insertion pattern has been used, so that the OFDM reception devicemay exactly detect pilot tones inserted in the used pilot insertionpattern and may use the detected pilot tones for channel equalizationand estimation. Accordingly, the control unit 130 may record pilotinsertion pattern information on some data tones in each of theplurality of OFDM symbols, and may transmit the information.Alternatively, the control unit 130 may record pilot insertion patterninformation on at least part of data tones used in part of the OFDMsymbols, and may transmit the information. The pilot insertion patterninformation may be represented by one bit or two bits. For example, 01,10, 11 and 00 are used as information to designate the first to fourthpilot insertion patterns, respectively.

FIG. 7 is a flowchart explaining an OFDM transmission method accordingto an exemplary embodiment of the present invention. The OFDMtransmission device generates a plurality of OFDM symbols (S710). Aprocess for generating OFDM symbols has been well known to those skilledin the art, so detailed description thereof is omitted.

The OFDM transmission device selects a pilot insertion pattern (S720).The pilot insertion pattern may be selected according to the type ofcommunication environment. In more detail, the OFDM transmission devicemay select a pilot insertion pattern according to whether the OFDMreception device is used in a dynamic or static communicationenvironment, or according to whether there is a need to transmithigh-capacity data. In this exemplary embodiment of the presentinvention, the OFDM transmission device may select a pilot insertionpattern from among the pilot insertion patterns shown in FIGS. 3 to 6.

Subsequently, the OFDM transmission device inserts pilot tones into theplurality of OFDM symbols in the selected pilot insertion pattern(S730). The plurality of OFDM symbols into which pilot tones areinserted according to the selected pilot insertion pattern are shown inFIGS. 3 to 6.

The OFDM transmission device sequentially transmits the plurality ofOFDM symbols into which the pilot tones are inserted (S740).Accordingly, it is possible to provide OFDM broadcasting with the datatransmission rate matching the communication environment.

FIG. 8 is a block diagram showing an OFDM reception device according toan exemplary embodiment of the present invention. The OFDM receptiondevice of FIG. 8 includes a receiving unit 210, a pilot insertionpattern determination unit 220 and an OFDM reception processing unit230.

The receiving unit 210 receives the plurality of OFDM symbols from anOFDM transmission device. The plurality of received OFDM symbols containpilot tones inserted thereinto based on a change in pilot insertionpatterns selected according to the type of communication environment, sothe data transmission rate is variable. Here, the OFDM transmissiondevice may have the configuration shown in FIG. 1 or 2.

The pilot insertion pattern determination unit 220 detects the pilotinsertion pattern information from the plurality of received OFDMsymbols. The pilot insertion pattern information is used to notify whichpilot insertion pattern has been used, so the pilot insertion patterndetermination unit 220 may determine the type of pilot insertion patternusing the detected information. One among the pilot insertion patternsshown in FIGS. 3 to 6 may be applied to the OFDM symbols, and pilotinsertion patterns having other forms may also be used. Each of thepilot insertion patterns may be designed in such a manner that pilottones are not inserted into a predetermined number of OFDM symbols inregular periods on the time axis while arrangement of pilot tones aremaintained on the frequency axis. Therefore, pilot insertion and pilotdetection processes may be performed in the same manner as theconventional DVB-T system.

The OFDM reception processing unit 230 detects pilot tones from the OFDMsymbols based on the determined pilot insertion pattern, and processesthe plurality of OFDM symbols. The configuration of the OFDM receptionprocessing unit 230 will be described in detail with reference to FIG.9.

FIG. 9 is a detailed block diagram showing the OFDM reception device ofFIG. 8. The OFDM reception device shown in FIG. 9 further includes astorage unit 240 in addition to the receiving unit 210, pilot insertionpattern determination unit 220 and OFDM reception processing unit 230.

The receiving unit 210 includes an analog-to-digital converter (ADC)211, a down converter 212 and an FFT processing unit 213. The receivingunit 210 receives the plurality of OFDM symbols from the OFDMtransmission device.

The ADC 211 converts analog data received via an antenna into digitaldata, and outputs the converted digital data.

The down converter 212 down-converts the digital data output from theADC 211 to a baseband signal.

The FFT processing unit 213 performs FFT processing on thedown-converted signal, and outputs frequency domain OFDM symbols.

The pilot insertion pattern determination unit 220 detects pilotinsertion pattern information from data tones contained in the OFDMsymbols output from the FFT processing unit 213, and determines whichpilot insertion pattern is applied to the currently received OFDMsymbol. Specifically, the pilot insertion pattern corresponding to thedetected information may be selected from the storage unit 240.

The storage unit 240 stores a plurality of pilot insertion patterns thathave been previously set between the OFDM reception device and OFDMtransmission device. In more detail, the storage unit 240 may store thepilot insertion patterns shown in FIGS. 3 to 6, so it is possible toimplement the same configuration as the conventional DVB-T standardhaving compatibility with the conventional DVB-T standard.

The pilot insertion pattern determination unit 220 sends the determinedpilot insertion pattern to the OFDM reception processing unit 230.

The OFDM reception processing unit 230 includes an equalizer 231 and anFEC decoder 232. The OFDM reception processing unit 230 processes eachof the plurality of OFDM symbols.

If the pilot insertion pattern is provided by the pilot insertionpattern determination unit 220, the equalizer 231 detects pilot tonesfrom the plurality of OFDM symbols, and equalizes the OFDM symbols usingthe detected pilot tones.

The FEC decoder 232 performs forward error correction processing on theequalized OFDM symbols. The receiving unit 210 and OFDM receptionprocessing unit 230 may be configured in the same manner as known tothose skilled in the art, so no further detailed description thereof isprovided.

FIG. 10 is a flowchart explaining an OFDM reception method according toan exemplary embodiment of the present invention. In FIG. 10, when theplurality of OFDM symbols are received from the OFDM transmission device(S1010), the OFDM reception device determines the position of pilottones, namely, the pilot insertion patterns, using the pilot insertionpattern information identified by certain data tones in the OFDM symbol(S1020).

Accordingly, the OFDM reception device detects the pilot tones accordingto the determined pilot insertion pattern, and performs equalizationprocessing on the OFDM symbols using the detected pilot tones (S1030).

Here, the pilot insertion pattern may be selected adaptivelycorresponding to an environment in which the OFDM reception devicereceives the OFDM symbols. For example, if the OFDM reception device isable to move in the dynamic communication environment, a pilot insertionpattern in which pilot tones are inserted into each of the plurality ofthe OFDM symbols, namely the fourth pilot insertion pattern shown inFIG. 6, may be used. Alternatively, taking into consideration the datatransmission rate, one of the first to third pilot insertion patternsmay be optionally selected. Additionally, the OFDM reception device maytransmit communication environment information to the OFDM transmissiondevice, or the communication environment information may be transferredto the OFDM transmission device by various ways.

Various pilot insertion patterns other than the pilot insertion patternsshown in FIGS. 3 to 6 may be used, for example, pilot insertion patternsshown in FIGS. 11 and 12.

Referring to FIG. 11, the OFDM transmission device may select a pilotinsertion pattern by adjusting the pilot insertion period n and thedistance m between a pilot insertion position in a current OFDM symboland a pilot insertion position in a previous OFDM symbol. In otherwords, while n is 12 and m is 3 in the pilot insertion patterns shown inFIGS. 3 to 6, either or both n and m may be adjusted so that the pilotinsertion pattern may also be adjusted.

For example, if it is necessary to increase the data transmission rate,that is, if a static communication environment is formed, the pilotinsertion unit 120 of the OFDM transmission device may set n or m to begreater.

FIG. 11 shows a pilot insertion pattern when n is set to 24 and m is setto 4. In this situation, the number of pilot tones may be extremelyreduced even when pilot tones are inserted into all of the OFDM symbols,so the data transmission rate may increase.

The control unit 130 may select a pilot insertion pattern in such amanner of adjusting n and m to correspond to the communicationenvironment. For example, if a dynamic communication environment isformed, the control unit 130 may select a first pilot insertion patternin which n is set to 6 and m is set to 2. Additionally, if a dynamiccommunication environment having low mobility is formed, the controlunit 130 may select a second pilot insertion pattern in which n is setto 12 or 16 and m is set to 3 or 4, so it is possible to ensure both thedata transmission rate and stability. Furthermore, if a staticcommunication environment without having mobility, the control unit 130may select a third pilot insertion pattern in which n is set to 24 and mis set to 4, as shown in FIG. 11. Accordingly, it is possible to adjustthe data transmission rate while pilot tones being inserted into all ofthe OFDM symbols on the time axis, differently from the pilot insertionpatterns shown in FIGS. 3 to 6.

Additionally, it is possible to adjust n and m while pilot tones are notinserted into part of OFDM symbols, so as to adjust the datatransmission rate. FIG. 12 shows a pilot insertion pattern according tosuch an exemplary embodiment.

In the pilot insertion pattern shown in FIG. 12, n is set to 24 and m isset to 6, and pilot insertion is skipped every third OFDM symbol.Alternatively, pilot insertion may be skipped according to use anddesign environment of the OFDM transmission and reception system.Additionally, n and m remain unchanged in a currently used systemenvironment, taking into consideration the pilot insertion period andposition difference, so the OFDM transmission and reception system mayhave compatibility with the conventional system. For example, if n isset to 20 and m is set to 5 in the conventional system, the OFDMtransmission and reception system of the present invention may changethe data transmission rate without any change in n and m, while pilottones being inserted into only some OFDM symbols.

Although a few exemplary embodiments of the present general inventiveconcept have been shown and described, it will be appreciated by thoseskilled in the art that changes may be made in these exemplaryembodiments without departing from the principles and spirit of thegeneral inventive concept, the scope of which is defined in the appendedclaims and their equivalents.

What is claimed is:
 1. An orthogonal frequency division multiplexing(OFDM) transmission device which transmits OFDM symbols to at least onereception device, the OFDM transmission device comprising: an OFDMtransmission processing unit which generates a plurality of OFDMsymbols; a pilot insertion unit which inserts pilot tones into each ofthe plurality of OFDM symbols; and a control unit which controls thepilot insertion unit to select a pilot insertion pattern to correspondto a communication environment from among a plurality of pilot insertionpatterns and insert the pilot tones according to the selected pilotinsertion pattern.
 2. The OFDM transmission device as claimed in claim1, wherein the pilot insertion unit inserts each pilot tone into asingle OFDM symbol every n-th tone so that the pilot tone on the OFDMsymbol is spaced apart from a pilot tone on a previous OFDM symbol by mtones, and wherein n and m are natural numbers.
 3. The OFDM transmissiondevice as claimed in claim 1, wherein one of the plurality of pilotinsertion patterns is formed on at least part of the plurality of OFDMsymbols, in which a single pilot tone is inserted into a single OFDMsymbol every 12-th tone so that the pilot tone is spaced apart from apilot tone on a previous OFDM symbol by 3 tones.
 4. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 12-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 6 tones.
 5. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 24-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 6 tones.
 6. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 24-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 12 tones.
 7. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 48-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 12 tones.
 8. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 48-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 24 tones.
 9. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 96-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 24 tones.
 10. The OFDMtransmission device as claimed in claim 1, wherein one of the pluralityof pilot insertion patterns is formed on at least part of the pluralityof OFDM symbols, in which a single pilot tone is inserted into a singleOFDM symbol every 96-th tone so that the pilot tone is spaced apart froma pilot tone on a previous OFDM symbol by 6 tones.
 11. An orthogonalfrequency division multiplexing (OFDM) transmission method whichtransmits OFDM symbols to at least one reception device, the OFDMtransmission method comprising: generating a plurality of OFDM symbols;selecting one pilot insertion pattern from among a plurality of pilotinsertion patterns according to a communication environment with the atleast one reception device; inserting pilot tones into each of theplurality of OFDM symbols according to the selected pilot insertionpattern; and transmitting the plurality of OFDM symbols to the at leastone reception device.
 12. The OFDM transmission method as claimed inclaim 11, wherein the inserting inserts each pilot tone into a singleOFDM symbol every n-th tone so that the pilot tone on the OFDM symbol isspaced apart from a pilot tone on a previous OFDM symbol by m tones, andwherein n and m are natural numbers.
 13. An orthogonal frequencydivision multiplexing (OFDM) reception device, the OFDM reception devicecomprising: a receiving unit which receives a plurality of OFDM symbols,of which the data transmission rate varies according to changes in pilotinsertion patterns; a pilot insertion pattern determination unit whichdetects pilot insertion pattern information contained in the pluralityof OFDM symbols, and determines which pilot insertion pattern is used inthe plurality of OFDM symbols using the detected information; and anOFDM reception processing unit which detects pilot tones from theplurality of OFDM symbols based on the determined pilot insertionpattern, and processes the plurality of OFDM symbols.
 14. The OFDMreception device as claimed in claim 13, further comprising: a storageunit which stores pilot insertion pattern information which is sharedwith an OFDM transmission device, wherein the pilot insertion patterndetermination unit reads the pilot insertion pattern information fromthe storage unit.
 15. The OFDM reception device as claimed in claim 13,wherein the reception unit receives a plurality of OFDM symbols, onlysome of which contain pilot tones, if a static communication environmentis established in which the OFDM reception device receives the pluralityof OFDM symbols while being fixed in place, and the reception unitreceives a plurality of OFDM symbols, each of which contains pilottones, if a dynamic communication environment is established in whichthe OFDM reception device receives the plurality of OFDM symbols whilemoving.
 16. The OFDM reception device as claimed in claim 13, whereinthe pilot insertion pattern is selected from among the plurality ofpilot insertion patterns in the OFDM transmission device to correspondto the type of communication environment.
 17. The OFDM reception deviceas claimed in claim 13, wherein each pilot insertion position is set byinserting each pilot tone into a single OFDM symbol every n-th tone sothat the pilot tone on the OFDM symbol is spaced apart from a pilot toneon a previous OFDM symbol by m tones, n and m are natural numbers, andpilot tones are inserted according to a pilot insertion pattern in whichat least one of n and m is adjusted corresponding to the type ofcommunication environment.
 18. The OFDM reception device as claimed inclaim 13, wherein one of the plurality of pilot insertion patterns isformed on at least part of the plurality of OFDM symbols, in which asingle pilot tone is inserted into a single OFDM symbol every 12-th toneso that the pilot tone is spaced apart from a pilot tone on a previousOFDM symbol by 3 tones or 6 tones.
 19. The OFDM reception device asclaimed in claim 13, wherein one of the plurality of pilot insertionpatterns is formed on at least part of the plurality of OFDM symbols, inwhich a single pilot tone is inserted into a single OFDM symbol every24-th tone so that the pilot tone is spaced apart from a pilot tone on aprevious OFDM symbol by 6 tones or 12 tones.
 20. The OFDM receptiondevice as claimed in claim 1, wherein one of the plurality of pilotinsertion patterns is formed on at least part of the plurality of OFDMsymbols, in which a single pilot tone is inserted into a single OFDMsymbol every 48-th tone so that the pilot tone is spaced apart from apilot tone on a previous OFDM symbol by 12 tones or 24 tones.
 21. TheOFDM reception device as claimed in claim 1, wherein one of theplurality of pilot insertion patterns is formed on at least part of theplurality of OFDM symbols, in which a single pilot tone is inserted intoa single OFDM symbol every 96-th tone so that the pilot tone is spacedapart from a pilot tone on a previous OFDM symbol by 24 tones or 6tones.
 22. An orthogonal frequency division multiplexing (OFDM)reception method in an OFDM reception device, the OFDM reception methodcomprising: receiving a plurality of OFDM symbols, of which the datatransmission rate varies according to changes in pilot insertionpatterns; detecting pilot insertion pattern information contained in theplurality of OFDM symbols, and determining which pilot insertion patternis used in the plurality of OFDM symbols using the detected information;and detecting pilot tones from the plurality of OFDM symbols based onthe determined pilot insertion pattern, and processing the plurality ofOFDM symbols.